This invention relates in general to drive train systems for transferring rotational power from an engine/transmission assembly to an axle assembly in a vehicle drive train system. In particular, this invention relates to an improved structure for precisely positioning a flange yoke on a companion flange that, in turn, is supported on a splined shaft in such a drive train system.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the is source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
The output shaft of the engine/transmission assembly is typically embodied as a male splined member that is generally cylindrical in shape and has a plurality of outwardly extending splines formed on the outer surface thereof. To connect the output shaft of the engine/transmission assembly to the front universal joint, a companion flange and flange yoke assembly is often provided. The companion flange and flange yoke assembly includes two physically separate components, namely, a companion flange and a flange yoke, that are secured together for concurrent rotational movement. The companion flange usually includes a hollow cylindrical sleeve portion and a disc-shaped flange portion. The sleeve portion of the companion flange has a plurality of inwardly extending splines formed on an inner surface thereof that cooperate with the outwardly extending splines of the male member so as to connect the sleeve portion to the output shaft of the engine/transmission assembly for rotational movement. The flange portion of the companion flange is formed integrally with the sleeve portion and has a plurality of apertures formed therethrough. The flange yoke usually includes a disc-shaped flange portion and a yoke portion. The flange portion of the flange yoke has a corresponding plurality of apertures formed therethrough that receive respective threaded fasteners to secure the flange yoke to the companion flange. The yoke portion of the flange yoke is formed integrally with the flange portion and has a pair of spaced apart yoke arms formed thereon that cooperate with a cross and the front end fitting of the driveshaft assembly to form the front universal joint.
As with all mechanical structures that physically engage one another, the precise positioning of the output shaft of the engine/transmission assembly, the companion flange, and the flange yoke relative to one another is limited by dimensional variations in the manufacture of each of these individual components. Thus, in the above-described structure, a first predetermined tolerance for such dimensional variations exists between the male splined output shaft of the engine/transmission assembly and the female splined companion flange that is mounted thereon. Additionally, a second predetermined tolerance for such dimensional variations exists between the companion flange and the flange yoke that is secured thereto. It has been found that in some instances, these first and second predetermined tolerances can, in the aggregate, introduce an undesirable amount of imprecision in the positioning of the output shaft of the engine/transmission assembly, the companion flange, and the flange yoke relative to one another. Such imprecise positioning can result in undesirable imbalances when the driveshaft assembly is rotated during use. Thus, it would be desirable to provide an improved structure for precisely positioning an output shaft of a engine/transmission assembly, a companion flange, and a flange yoke relative to one another to minimize such imbalances.